on my 257wby , 20 year ago , i use only imr-4350 and 100grs bullets, on a barrel of 24" a get 3470fps average 10 shots and the weatherby cases works nice for 8 reloads, the load of 66.0grs of 4350 and primer cci-250 and 100grs bullets is very accurate.
now i use imr-7828 on all my weatherbys...